Manufacture of printing forms



H. C. MOOG Mai 20, 1958 MANUFACTURE OF PRINTING FORMS 3 Sheets-Sheet 1 Filed June 27,- 1955 //V [/5 N TOR f/errr/ C. ag: 1

A TORNE Y y 20, 1958 H. c. MOOG 2,834,985

MANUFACTURE OF PRINTING FORMS Filed June 27, 1955 3 Sheets-Sheet 2 28 11 27 73 I2 IO 10 9 I5 Figs 11 27 N 3 /1 g l YNVENTOR %'/7/7 C./70 0 jf ATTORNEY Unite States Patent MANUFACTURE OF PRINTING FORMS Henry Cornelius Moog, Geisenheim, Germany, assignor to Leathley Publications Limited, London, England Application June 27, 1955, Serial No. 518,174

4 Claims. (Cl. 18-19) The present invention relates to the manufacture of cylindrical printing forms by the use of a die under heat and pressure.

It has been proposed already to manufacture cylindrical printing forms by providing two semi-cylindrical dies and pressing these together over a cylinder whilst raising the temperature of the cylinder to a predetermined value. The outer surface of the cylinder is provided with a layer of suitable material such as thermoplastic material or unvulcauised rubber to take the impression from the dies.

This method has the disadvantage, however, that different dies are required for pressing cylindrical printing forms of different diameters. Furthermore the use of two semi- 2,834,935 Patented May 20, 1958 ice Fig. 4 is a perspective view of the press with the assembly of parts therein,

Fig. 5 is a perspective view of a pressure element of the press,

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 4,

Fig. 7 is a cross-sectional view taken on the line 7--7 of Fig. 6,

Fig. 8 is a cross-sectional View of a modified part of the press.

In Fig. 1 a steel cylinder 10, an unvulcauised rubber sheet 11, a flexible photogravure die 12, a brass sheet 13 cylindrical dies in this way is not always satisfactory since two seams are liable to be formed between the abutting edges of the semi-cylindrical dies and hence faulty forms can readily result.

One object of the present invention is to provide an improved method of manufacturing cylindrical printing -forms by the use of heat and pressure whereby the aforesaid disadvantage can be overcome.

According to the present invention a method of manufacturing a cylindrical printing form comprises the steps of providing a hollow cylinder with an outer layer of material suitable for taking an imprint under the action of heat and pressure, wrapping a flexible die around the cylinder, wrapping around the die a pressure element in the form of a flexible rectangular sheet having fingers formed in two opposite ends thereof, drawing the fingers of one end of the sheet between the fingers of the other end, and heating the cylinder from. within. The cylinder must of course be of sulficient strength to withstand the pressure applied by the pressure element. The flexible die may conveniently be in the form of a sheet of metal on which is formed a relief of the imprint to be made. The cylinder can be heated from within by various means such as passing hot gas or vapour through the cylinder or by the use of an electric heating element mounted within the cylinder. It is preferred to close the ends of the cylinder by means of cones and to pass steam through the cylinder by way of entry and exit ports in the cones.

The invention also provides a press for carrying out the method, the press comprising a rectangular flexible sheet having fingers formed in two opposite ends thereof, means for drawing the fingers of one end between the fingers of the other end whereby pressure can be exerted upon cylinders of different diameters depending upon the extent of inter-engagement of the fingers and means for heating a cylinder under pressure.

The invention will now be described by way of example with reference to the accompanying drawings in which Fig. 1 shows a number of parts to be assembled and pressed to form a cylindrical photogravure printing form,

Fig. 2 shows the form produced from the parts of Fig. 1,

Fig. 3 is a cross-sectional view of the parts of Fig. l assembled in a press,

and a strip 14 of metal are to be assembled and employed to form a cylindrical printing form as shown in Fig. 2.

Referring to Fig. 3, the rubber sheet 11 is wrapped around the steel cylinder 10 with the two ends of the rubber sheet overlapping as shown at 15. The flexible die 12 is wrapped around the rubber sheet 11 and it is arranged that the two ends of the die substantially meet. At the small gap between the abutting ends of the die the strip 14 of metal is placed between the rubber and the die for the purpose of preventing rubber from squeezing up into the gap during a subsequent pressing operation. The brass sheet 13 is wrapped around the die and as shown in Fig. 3 it is arranged that the two ends of the brass sheet 13 almost meet one another.

This assembly of parts 10 to 15 is now ready for pressing in a press of which a perspective view is shown in Fig. 4. The press comprises a main frame 16 which carries two hydraulic rams 17 and 18, and a member 19 which is slidably mounted in guides 20. A flexible sheet 21 also shown in Fig. 5 is of rectangular shape and has fingers 22 formed in two opposite ends thereof. The two sets of fingers are welded to two plates 23 and 24 respectively and the plate 23 is bolted to the frame 16 by means of bolts 25. The other plate 24 is bolted to the slidable member 19 by means of further bolts of which one is shown in Fig. 6 at 26.

When the hydraulic rams are operated the plate 24 is forced away from the plate 23 thereby drawing the fingers attached tothe plate 24- between the fingers attached to the plate 23 until the assembly to parts 18 to 15 is put under pressure as shown in Fig. 6.

For the purpose of heating the cylinder 10 two cones 27 and 28 are provided one at each end of the cylinder, as shown in Fig. 7. These cones are urged toward one another by means of threaded rods 29 and nuts 30 and 31 whereby the cylinder can be sealed. Steam is fed into the cylinder through a port 32 in the cone 28 and leaves the cylinder through a port 33 in the cone 27 The cone 28 is arranged to be hollow and a thermometer 34 (Fig. 4) is inserted into the hollow cone. Steam is fed to the cylinder through a pipe 32 from a boiler (not shown) and the steam leaving the cylinder may be carried by a pipe 33 to a condenser (not shown).

When the rubber is vulcanised the steam is shut off and the press allowed to cool. The pressure is then released,and the cylinder 10 carrying the rubber layer 11 is removed. The vulcanised layer 11 now carries an imprint of the die 12 and is ready for use.

It will be appreciated that by using cones as shown in Fig. 7 cylinders of different diameters can be accommodated. The range of cylinder diameter-s that can be accommodated can be increased as shown in Fig. 8 by adding further cones such as the cone 35.

The brass sheet 13 may conveniently be of about 20 gauge and the strip 14 of metal may conveniently be about 2 or 3 thousandths of an inch in thickness.

In producing the photogravure die 12 it is preferred to use a method in which a screened negative is printed down on to a carbon tissue having an additional gelatin layer between the .paper and the -main gelatin layer. T-his additional gelatin layer is heavily pigmented with black pigment to make it opaque. Thus when printing down on tothe-carbon tissue the lighbdoes not penetrate beyond the pigmented layer. After exposurethe gelatin *surfa'ce of the earbon -tissue is afiiXed to-abrass-isheet and' the tissue is washed in warm water to remove the paper. The :pigmented layer and 'the unexposed partsof the main gelatin layer are then developed and the -whole is dried to form the die.

stood'by those-skilled in the: art thetype of form produced is dependent upon the die employed.

'1 claim:

1. A method of manufacturin-g 'a cylindricalprinting formicompn'sing the steps-of providing 'ahollow cylinder with an outer layer of material suitable .fortakin'g an imprint underthe action of "heat and pressure, Wrapping a ficxibledie around-the cylinder, wrapping aroun dthe die a pressureapplying element in the formof'afiexible rectangular sheet having fingers "formed in two opposite ends thereof, drawing the fingers of "one endof the sheet "between thefingers of'theother end to contact the 4 sheet "about said die and layer, and a heating thecylinder from within.

2. A method according to claim 1 wherein the heating is effected by passing heated gas or vapour through the cylinder.

3. A press having, in combination, means for receiving a hollow cylinder, means-for heating said cylinder from within, :and .a pressure applying device for embracing and applying pressure upon the cylinder, said device being in the form =df a rectangular flexible sheet having a principal-pressure applying A portion' of rectangular "shape with a plunalityof-fingers formed in two opposite ends thereof, and having a means for drawing the fingers of one end betweeni'the'fingers of the-other end, whereby contractile pressure can be exerted upon cylinders of different diameters depending upon the extent of interengagement of the fingers.

4. 'A-press according toclaim 3, wherein theheating meanscomprise-two cones which fit intothe two ends respectively of the cylinders and means for passingsteam through thecylinder by wayof p0rts inthe tw0 cones.

. References cited inthe file.of. this patent UNITED STATES PATENTS 553,877 .:Stowe Feb. 4, :1896 1,950,678 Hogan Mar. .13, 1934 2,251,047 .Ganglofi July v2.9, .1941 2,333,800 Lewiset al Nov. 9,1943 

